how much energy bring to us. john: but the u.s. department of health says a calorie is a calorie. >> it just hasn't been tested. one of the things we did when i started this organization. john: this being? >> the nutritionist study. we went back to world war ii to every scientist that attempted to answer that question. we found 82 studes that have attempteto answer that. they were all probably the same limitations and problems. in 2012, there is plenty of anecdotal evidence. a calorie is not a calorie, necessarily. john: one thing that absolutely must be true if you should eat less fat. yet you eat lots of fat. and you're a doctor. a stanford doctor. what's that about? >> like i said, three or four years ago, when i got t the point where ms. chu overweight and my wife said i needed to be a little less not so thin, i realized that i probably had a carbohydrate intolerance issues in all of whole grains and things that i was eating were probably leading to be becoming fatter. and if i tripped that stuff out of my diet and i ate more f